1. Field of the Invention
The present invention relates generally to the field of mechanisms for transmitting rotational energy and torque from one mechanical element to another. More specifically the present invention relates to a transmission apparatus for transmitting rotational energy from an input shaft to an output shaft at gear ratios, or in more general terms at rotational ratios, which are variable between a maximum forward ratio and a maximum rearward ratio continuously at any of an infinite number of intermediate ratios.
The apparatus includes a ring gear having internal ring gear teeth and having a central axis. The ring gear is constrained with ring gear constraining means to move translationally along a lateral circular path about an input shaft rotational axis, without rotating about its own central axis relative to the apparatus; means for continuously changing the distance between the ring gear central axis and the input shaft rotational axis; a pinion gear having a diameter smaller than the inner diameter of the ring gear and retained with the ring gear such that its rotational axis is parallel with the ring gear central axis and held in engagement with the ring gear teeth by pinion gear constraining means connected to an apparatus output shaft by gear train means to transmit torque and rotational movement to the output shaft.
2. Description of the Prior Art
There have long been transmissions for transmitting torque from an input shaft to an output shaft and for altering the number of revolutions made by the output shaft for every revolution of the input shaft. Examples of these prior transmissions are found in automobiles and plant machinery. A problem with them is that most alter the rotational ratios incrementally, by disengaging the input shaft momentarily to permit shifting a new gear into the chain. This shifting causes discontinuous acceleration and requires either complex and expensive automatic shifting mechanisms or human monitoring and control. Furthermore, the clutches wear out much faster than the transmission as a whole, making frequent shut-downs and servicing necessary.
Continuously variable transmissions have been constructed, but with decided disadvantages. An example is a rotating disk having a radially mounted engaging wheel which slides along the disk to varying radial points for different disk/wheel rotational ratios. This transmission is used in some lawn mowers, and has proven inefficient and subject to frequent failure. Others have involved complicated fluid pump braking systems, and can be heavier, bulkier and more expensive to manufacture than conventional, shifting transmissions.
Prior art references for transmissions generally which are known to the applicant include: German U.S. Pat. No. 3,532,736, having an output on sliding blocks; Irvin, U.S. Pat. No. 5,099,706, having a rack and pinion drive transmission; France U.S. Pat. No. 1,251,574, having an eccentric planetary drive; Koser U.S. Pat. No. 4,497,221, varying the radius of the chain ring so as to vary the ratio; Pires U.S. Pat. No. 5,108,352, having an eccentric planetary transmission with a counterbalance means and sliding blocks; and Rhodes U.S. Pat. No. 1,701,823, having a CVT using centrifugal force to change ratio, and having a rotating ring gear.
It is thus an object of the present invention to provide a transmission which provides clutch-free, continuously variable transmission of torque.
It is another object of the present invention to provide such a transmission which is simple in design, having only a few operating parts, and is reliable and inexpensive to build.
It is still another object of the present invention to provide such a transmission which can be serviced easily and by minimally skilled personnel.
It is finally an object of the present invention to provide such a transmission which occupies less space than most automatic transmissions in use today.